Sensitization to another anticancer therapy and/or amelioration of a side effect of another anitcancer therapy by treatment with a GST-activated anticancer compound

ABSTRACT

A method of sensitizing a mammal, especially a human, to another anticancer therapy by administering a sensitizing effective amount of a GST-activated anticancer compound. A method of ameliorating a side effect of another anticancer therapy in a mammal, especially a human, by administering an ameliorating effective amount of a GST-activated anticancer compound. Pharmaceutical compositions for the methods. The GST-activated anticancer compound is preferably a compound of U.S. Pat. No. 5,556,942, and more preferably canfosfamide, especially as the hydrochloride salt.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. 119(e) of U.S.Provisional Application No. 60/572,790, filed 20 May 2004, which isincorporated into this application by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to anticancer therapy.

2. Description of the Related Art

The purpose of anticancer therapy is to prevent cancer cells frommultiplying, invading, metastasizing, and ultimately killing their hostorganism, e.g. a human or other mammal. Because cell multiplication is acharacteristic of many normal cells as well as cancer cells, mostanticancer therapies also have toxic effects on normal cells,particularly those with a rapid rate of turnover, such as bone marrowand mucous membrane cells. The goal in selecting an effective anticancertherapy, therefore, is to find a therapy that has a marked growthinhibitory or controlling effect on the cancer cells and a minimal toxiceffect on the host. In the most effective therapies, the agents used arecapable not only of inhibiting but also eradicating all cancer cellswhile sufficiently preserving normal cells to permit the host to returnto normal or at least satisfactory life function and quality. Anticancertherapies include classic chemotherapy with antiproliferative agents(typically, small molecules) that target all dividing cells; moleculartargeted therapy designed to specifically target cancer cells, such asfunctional therapy designed to alter a molecular function in the cancercells with gene therapy, antisense therapy, and drugs such as erlotinibhydrochloride, gefitinib, and imatinib mesylate, and phenotype-directedtherapy designed to target the unique phenotype of cancer cells such astherapy with monoclonal antibodies, immunotoxins, radioimmunoconjugates,and cancer vaccines; biologic therapy with cytokines such asinterleukin-2 and interferon-α; and radiotherapy.

However, although the first effective anticancer compounds were broughtinto clinical trials in the 1940's, initial therapeutic results weredisappointing. Regressions of acute lymphocytic leukemia and adultlymphomas were obtained with single agents such as the nitrogenmustards, antifolates, corticosteroids, and vinca alkaloids, butresponses were frequently partial and only of short duration; andrelapse was associated with resistance to the original drug. Initialresistance to a given single agent (natural resistance) is frequent, andeven initially responsive cancers frequently display acquired resistanceafter drug exposure, probably owing to selection of pre-existingresistant cancer cells from a heterogeneous population and possibly alsoowing to an increased rate of mutation to resistance. This is consistentwith the clinical observation that, with few exceptions, cancers arecured only by combination therapy. Cancers are frequently characterizedas being resistant (not showing a response during the initial course oftherapy) or refractory (having shown an initial response, then relapsed,and not showing a response on a later course of therapy) to anticancertherapies. Resistance to one anticancer drug, e.g. a platinum anticancercompound such as cisplatin, is often associated with cross-resistance toother drugs of the same class, e.g. other platinum compounds. Multipledrug resistance, also called pleiotropic drug resistance, is aphenomenon where treatment with one drug confers resistance not only tothat drug and others of its class but also to unrelated agents.

Anticancer therapies, especially chemotherapies, are frequently employedin combination, for several principal reasons. First, treatment with twoor more non-cross-resistant therapies may prevent the formation ofresistant clones; second, the combination of two or more therapies thatare active against cells in different phases of growth (resting—G₀,postmitotic—G₁, DNA synthesis—S, premitotic—G₂, and mitotic—M) may killcells that are dividing slowly as well as those that are dividingactively and/or recruit cells into a more actively dividing state,making them more sensitive to many anticancer therapies; and third, thecombination may create a biochemical enhancement effect by affectingdifferent pathways or different steps in a single biochemical pathway.Particularly when the toxicities of the therapies are non-overlapping,two or more therapies may be employed in full or nearly full amounts,and the effectiveness of each therapy will be maintained in thecombination; thus, myelosuppressive drugs may be supplemented bynon-myelosuppressive drugs such as the vinca alkaloids, prednisone, andbleomycin; and combination chemotherapies have been developed for anumber of cancers that are not curable with single agents. Combinationsof two or more of chemotherapy, molecular targeted therapy, biologictherapy, and radiotherapy are also known and used. Although theexistence of a wide variety of mechanistically distinct anticancertherapies suggests that non-cross-resistant therapies can be found,cancer cells are known to possess a variety of mechanisms that conferpleiotropic drug resistance. These mechanisms of resistance contributeto the failure of combination therapy to cure common cancers such asmetastatic colon cancer and prostate cancer.

A disadvantage of virtually all anticancer therapies is the occurrenceof side effects, undesired effects caused by the anticancer therapy on apatient being treated for a cancer. While some effects are minor intheir effect on the physical health of the patient, such as alopecia(which is common in patients treated with platinum compounds, taxanes,and anthracyclines), most others such as nausea, vomiting, andneutropenia (also common in patients treated with platinum compounds)can have such an effect on the physical health of the patient that theiroccurrence limits the ability to treat the patient with the desiredamount of the anticancer therapy and/or the willingness of the patientto undertake the anticancer therapy. Protective and adjunctive agents(as discussed in paragraph [0038] below) and antiemetics can be used toameliorate some of the side effects of some anticancer therapies;however, in many instances, anticancer therapy is administered not atthe amount that would be maximally effective against the cancer cellsthemselves, but in an amount at which the side effects of the therapyare tolerable or treatable, the maximum tolerated dose.

Discussions of anticancer chemotherapy and biologic therapy, and theirside effects, and examples of suitable therapeutic protocols, may befound in such books as Cancer Chemotberapy and Biotherapy: Principlesand Practice, 3rd ed. (2001), Chabner and Longo, eds., and Handbook ofCancer Chemotherapy, 6th ed. (2003), Skeel, ed., both from LippincottWilliams & Wilkins, Philadelphia, Pa., U.S.A.; and regimens foranticancer therapies, especially chemotherapies, may be found on Websites such as those maintained by the National Cancer Institute(www.cancer.gov), the American Society for Clinical Oncology(www.asco.org), and the National Comprehensive Cancer Network(www.nccn.org).

Glutathione (GSH), in its reduced form, is a tripeptide of the formula:65 -L-Glu-L-Cys-Gly. Reduced glutathione has a central role inmaintaining the redox condition in cells and is also an essentialsubstrate for glutathione S-transferase (GST). GST exists in mammals asa superfamily of isoenzymes which regulate the metabolism anddetoxification of foreign substances introduced into cells. In general,GST can facilitate detoxification of foreign substances (includinganticancer drugs), but it can also convert certain precursors into toxicsubstances. The isoenzyme GST P1-1 is constitutively expressed in manycancer cells, such as ovarian, non-small cell lung, breast, colorectal,pancreatic, and lymphoma tissue (more than 75% of human tumor specimensfrom breast, lung, liver, and colorectal cancers are reported to expressGST P1-1). It is frequently overexpressed in tumors following treatmentwith many chemotherapeutic agents, and is seen in cancer cells that havedeveloped resistance to these agents.

U.S. Pat. No. 5,556,942 discloses compounds of the formula

and their amides, esters, and salts, where:

-   L is an electron withdrawing leaving group;-   S^(x) is —S(═O)—, —S(═O)₂—, —S(═NH)—, —S(═O)(═NH)—, —S+(C₁-C₆    alkyl)—, —Se(═O)—, —Se(═O)₂—, —Se(═NH)—, or —Se(═O)(═NH)—, or is    —O—C(═O)—, or —HN—C(═O)—;-   each R¹, R² and R³ is independently H or a non-interfering    substituent;-   n is 0, 1 or 2;-   Y is selected from the group consisting of-   where m is 1 or 2; and-   AA_(c) is an amino acid linked through a peptide bond to the    remainder of the compound, and their syntheses.

The compounds of the patent are stated to be useful drugs for theselective treatment of target tissues which contain compatible GSTisoenzymes, and simultaneously elevate the levels of GM progenitor cellsin bone marrow. Disclosed embodiments for L include those that generatea drug that is cytotoxic to unwanted cells, including thephosphoramidate and phosphorodiamidate mustards.

One of the compounds identified in the patent has the formula

It is referred to in the patent as TER 286 and named asγ-glutamyl-α-amino-β-((2-ethyl-N,N,N,N-tetra(2′-chloro)ethylphosphoramidate)sulfonyl)propionyl-(R)-(-)phenylglycine.This compound, later referred to as TLK286, has the CAS nameL-γ-glutamyl-3-[[2-[[bis[bis(2-chloroethyl)-amino]phosphinyl]oxy]ethyl]sulfonyl]-L-alanyl-2-phenyl-(2R)-glycine.As the neutral compound, its proposed International Nonproprietary Nameis canfosfamide; and as its hydrochloride acid addition salt, its UnitedStates Adopted Name is canfosfamide hydrochloride. Canfosfamide and itssalts are anticancer compounds that are activated by the actions of GSTP1-1, and by GST A1-1, to release the cytotoxic phosphorodiamidatemustard moiety.

In vitro, canfosfamide has been shown to be more potent in the M6709human colon carcinoma cell line selected for resistance to doxorubicinand the MCF-7 human breast carcinoma cell line selected for resistanceto cyclophosphamide, both of which overexpress GST P1-1, over theirparental cell lines; and in murine xenografts of M7609 engineered tohave high, medium, and low levels of GST P1-1, the potency ofcanfosfamide hydrochloride was positively correlated with the level ofGST P-1 (Morgan et al., Cancer Res., 58:2568 (1998)).

Canfosfamide, as its hydrochloride salt, is currently being evaluated inmultiple clinical trials for the treatment of ovarian, breast, non-smallcell lung, and colorectal cancers. It has demonstrated significantsingle agent antitumor activity and improvement in survival in patientswith non-small cell lung cancer and ovarian cancer, and single agentantitumor activity in colorectal and breast cancer. Evidence from invitro cell culture and tumor biopsies indicates that canfosfamide isnon-cross-resistant to platinum, paclitaxel, and doxorubicin (Rosario etal., Mol. Pharmacol., 58:167 (2000)), and also to gemcitabine. Patientstreated with canfosfamide hydrochloride show a very low incidence ofclinically significant hematological toxicity.

Other compounds specifically mentioned within U.S. Pat. No. 5,556,942are TLK231 (TER 231),L-γ-glutamyl-3-[[2-[[bis[bis(2-chloroethyl)amino]phosphinyl]oxy]ethyl]sulfonyl]-L-alanyl-glycine,activated by GST M1a-1a; TLK303 (TER 303),L-γ-glutamyl-3-[[2-[[bis[bis(2-chloroethyl)-amino]phosphinyl]oxy]ethyl]sulfonyl]-L-alanyl-2-phenyl-(2S) -alanine, activated by GST A1-1; TLK296 (TER 296),L-γ-glutamyl-3-[[2-[[bis[bis(2-chloroethyl)amino]phosphinyl]oxy]ethyl]sulfonyl]-L-phenylalanyl-glycine,activated by GST P1-1; and TLK297 (TER 297), L-γ-glutamyl-3-[[2-[[bis[bis(2-chloroethyl)amino]phosphinyl]oxy]ethyl]sulfonyl]-L-phenylalanyl-2-phenyl-(2R)-glycine,and their salts.

The disclosure of U.S. Pat. No. 5,556,942, and the disclosures of otherdocuments referred to in this application, are incorporated into thisapplication by reference.

Anticancer therapies are steadily evolving, but it remains true thateven the best current therapies are not always even initially effectiveand frequently become ineffective after treatment, and are frequentlyaccompanied by significant side effects, so that improved anticancertherapies are constantly being sought.

SUMMARY OF THE INVENTION

In a first aspect, this invention is a method of sensitizing a mammal,especially a human, to another anticancer therapy, that is, ananticancer therapy that is not a treatment with a GST-activatedanticancer compound (including chemotherapy; molecular targeted therapy;biologic therapy; and radiotherapy, used as monotherapy or incombination), comprising administering a sensitizing effective amount ofa GST-activated anticancer compound to the mammal.

In a second aspect, this invention is a pharmaceutical composition forsensitizing a mammal, especially a human, to another anticancer therapy,comprising a GST-activated anticancer compound and optionally anexcipient.

In a third aspect, this invention is a method of ameliorating a sideeffect of another anticancer therapy in a mammal, especially a human,comprising administering an ameliorating effective amount of aGST-activated anticancer compound to the mammal.

In a fourth aspect, this invention is a pharmaceutical composition forameliorating a side effect of another anticancer therapy in a mammal,especially a human, comprising a GST-activated anticancer compound andoptionally an excipient.

In preferred embodiments of this invention (preferred embodiments of themethods, compositions, and uses of this invention as mentioned inparagraphs [0017] through [0020] above), the GST-activated anticancercompound is a compound that is an inhibitor, especially an irreversibleinhibitor, of one or more GST isoenzymes and/or is a compound of U.S.Pat. No. 5,556,942, especially canfosfamide or an amide, ester,amide/ester, or salt thereof, particularly canfosfamide or a saltthereof, especially canfosfamide hydrochloride; and these preferencesand preferred another anticancer therapies for which the sensitizationby the GST-activated anticancer compound may be used are characterizedby the specification and by the features of method claims 1 through 36of this application as filed.

In a particular embodiment of the invention, the sensitization therapyof this invention excludes sensitization to oxaliplatin by canfosfamideand its salts, especially canfosfarmide hydrochloride, and/or excludessensitization to paclitaxel or sensitization to taxanes by canfosfamideand its salts, especially canfosfamide hydrochloride, and/or excludessensitization by canfosfamide and its salts, especially canfosfamidehydrochloride, at a dose of 500 mg/m² or more.

In another particular embodiment of this invention, the ameliorationtherapy excludes amelioration of a side effect of another anticancertherapy by canfosfamide and its salts, especially canfosfamidehydrochloride, at a dose of 500 mg/m² or more.

DETAILED DESCRIPTION OF THE INVENTION

The GST-Activated Anticancer Compound

A “GST-activated anticancer compound” is a compound comprisingglutathione or a glutathione analog chemically linked to a cytotoxicmoiety such that the cytotoxic moiety is released by cleavage from theglutathione or glutathione analog in the presence of one or more GSTisoenzymes.

Suitable such compounds include those disclosed in U.S. Pat. No.5,556,942 and are of the formula

and their amides, esters, and salts, where:

-   L is a cytotoxic electron withdrawing leaving group;-   S^(x) is —S(═O)—, —S(═O)₂—, —S(═NH)—, —S(═O)(═NH)—, —S+(C₁-C₆    alkyl)—, —Se(═O)—, —Se(═O)₂—, —Se(═NH)—, or —Se(═O)(═NH)—, or is    —O—C(═O)—, or —HN—C(═O)—;-   each of R¹, R² and R³ is independently H or a non-interfering    substituent, such as H, optionally substituted C₁-C₆ alkyl (for    example, methyl, tert-butyl, cyclohexyl, and the like), optionally    substituted C₆-C₁₂ aryl (for example, phenyl, naphthyl, pyridyl, and    the like), optionally substituted C₇-C₁₂ aralkyl (for example,    benzyl, phenylethyl, 2-pyridylethyl, and the like), cyano, halo,    optionally substituted C₁-C₆ alkoxy, optionally substituted C₆-C₁₂    aryloxy, or optionally substituted C₇-C₁₂ aralkoxy, where the    substituents may be halo, —OR, —SR, or —NR₂, where R is H or C₁-C₄    alkyl;-   n is 0, 1 or 2;-   Y is selected from the group consisting of    where m is 1 or 2; and-   AA_(c) is an amino acid linked through a peptide bond to the    remainder of the compound.

In preferred embodiments, one or more of the following preferences ismet: L is a toxin such as ricin or diphtheria toxin, a linkableanticancer agent such as doxorubicin or daunorubicin, or aphosphoramidate or phosphorodiamidate mustard, especially aphosphorodiamidate mustard of the formula —OP(═O)(NHCH₂CH₂X)₂ or—OP(═O)(N(CH₂CH₂X)₂)₂, particularly of the formula —OP(═O)(N(CH₂CH₂)₂)₂,where X is Cl or Br, especially Cl;

-   S^(x) is —S(═O)₂—;-   R¹ is H, C₁-C₄ alkyl, or phenyl, especially H or phenyl,    particularly H;-   each R² is independently chosen from H and C₁-C₆ alkyl, especially    H;-   each R³ is independently chosen from H, C₁-C₄ alkyl, and phenyl,    especially H;-   n is 0;-   Y—C(═O)— is γ-glutamyl;-   AA_(c) is glycine, phenylglycine, β-alanine, alanine, phenylalanine,    valine, 4-aminobutyric acid, aspartic acid, histidine, tryptophan,    and tyrosine, as either the (S)— or (R)—isomers, optionally    substituted on the phenyl ring as described above for R¹ through R³,    especially glycine, phenylglycine, β-alanine, alanine, or    phenylalanine, and particularly (R)-phenylglycine.

Suitable amides and esters of these compounds include those in which oneor more of the carboxyl groups is amidated or esterified to form a C₁-C₆alkyl or alkenyl, C₆-C₁₀aryl, or C₇-C₁₂ aralkyl amide or ester, in whichthe alkyl or aryl groups may be optionally substituted withnoninterfering substituents such as halo, alkoxy, or alkylamino. Theamides and esters may be monoamides or diamides, monoesters or diesters,or monoamide-monoesters. Suitable salts (see Berge et al., J. Pharm.Sci., 66:1 (1971) for a nonexclusive list) are those formed wheninorganic bases (e.g. sodium, potassium, and calcium hydroxide) ororganic bases (e.g. ethanolamine, diethanolamine, triethanolamine,ethylenediamine, tromethamine, N-methylglucamine) react with thecarboxyl groups, and those formed when inorganic acids (e. ghydrochloric, hydrobromic, sulfuric, nitric, and chlorosulfonic acids)or organic acids (e.g. acetic, propionic, oxalic, malic, maleic,malonic, fuimaric, or tartaric acids, and alkane- or arenesulfonic acidssuch as methanesulfonic, ethanesulfonic, benzenesulfonic, substitutedbenzenesulfonic such as chlorobenzenesulfonic and toluenesulfonic,naphthalenesulfonic and substituted naphthalenesulfonic,naphthalenedisulfonic and substituted naphthalenedisulfonic, andcamphorsulfonic acids) react to form acid addition salts of the aminegroups. Monoamide-monoester salts and ester salts are also included, asare hydrates and other solvates as well as unsolvated forms.

The preparation of these compounds and their derivatives may be made bymethods well known to the person of ordinary skill in the art and asdescribed in U.S. Pat. No. 5,556,942.

A particularly preferred GST-activated anticancer compound iscanfosfamide or its salts, especially canfosfamide hydrochloride.

As a monotherapy for a number of cancers, including ovarian, breast,non-small cell lung, and colorectal cancers, canfosfamide hydrochloridehas been administered by intravenous infusion at doses of 400-1000 mg/m²body surface area at once/week and once/three weeks.

As a combination therapy with cisplatin (75 and 100 mg/m²), canfosfamidehydrochloride has been administered at 750 and 1000 mg/M² at 3-weeklyintervals. As a combination therapy with carboplatin (AUC 5 or 6mg/mL·min), canfosfamide hydrochloride has been administered at 500,750, and 960 mg/M² at 3- to 4-weekly intervals. As a combination therapywith docetaxel (75 mg/m²), canfosfamide hydrochloride has beenadministered at 500, 750, and 960 mg/M² at 3-weekly intervals. As acombination therapy with liposomal doxorubicin (40 or 50 mg/m²),canfosfamide hydrochloride has been administered at 500, 750, and 960mg/m² at 4-weekly intervals. As a combination therapy with paclitaxel(200 mg/m² and carboplatin (AUC 6 mg/mL.min), canfosfamide hydrochloridehas been administered at 400, 500, 750, and 1000 mg/m² at 3-weeklyintervals.

Another Anticancer Therapy

“Another anticancer therapy” is an anticancer therapy that is not atreatment with a GST-activated anticancer compound, especially ananticancer therapy that is not a treatment with a compound disclosed inparagraphs [0025] to [0030] above. Such “another anticancer therapies”include chemotherapy, molecular targeted therapy, biologic therapy, andradiotherapy. These therapies are those used as monotherapy or incombination therapy.

Chemotherapeutic agents include:

-   alkylating agents, including:-   alkyl sulfonates such as busulfan,-   ethyleneimine derivatives such as thiotepa,-   nitrogen mustards such as chlorambucil, cyclophosphamide,    estramustine, ifosfamide, mechlorethamine,-   melphalan, and uramustine,-   nitrosoureas such as carmustine, lomustine, and streptozocin,-   triazenes such as dacarbazine, procarbazine, and temozolamide, and-   platinum compounds such as cisplatin, carboplatin, oxaliplatin,    satraplatin, and picoplatin;-   antimetabolites, including:-   antifolates such as methotrexate, permetrexed, raltitrexed, and    trimetrexate,-   purine analogs such as cladribine, chlorodeoxyadenosine,    clofarabine, fludarabine, mercaptopurine,-   pentostatin, and thioguanine,-   pyrimidine analogs such as azacitidine, capecitabine, cytarabine,    edatrexate, floxuridine, fluorouracil,-   gemcitabine, and troxacitabine;-   natural products, including:-   antitumor antibiotics such as bleomycin, dactinomycin, mithramycin,    mitomycin, mitoxantrone,-   porfiromycin, and anthracyclines such as daunorubicin (including    liposomal daunorubicin), doxorubicin (including liposomal    doxorubicin), epirubicin, idarubicin, and valrubicin,-   enzymes such as L-asparaginase and PEG-L-asparaginase,-   microtubule polymer stabilizers such as the taxanes paclitaxel and    docetaxel,-   mitotic inhibitors such as the vinca alkaloids vinblastine,    vincristine, vindesine, and vinorelbine,-   topisomerase I inhibitors such as the camptothecins irinotecan and    topotecan, and-   topoisomerase II inhibitors such as amsacrine, etoposide, and    teniposide;-   hormones and hormone antagonists, including:-   androgens such as fluoxymesterone and testolactone,-   antiandrogens such as bicalutamide, cyproterone, flutamide, and    nilutamide,-   aromatase inhibitors such as aminoglutethimide, anastrozole,    exemestane, formestane, and letrozole,-   corticosteroids such as dexamethasone and prednisone,-   estrogens such as diethylstilbestrol,-   antiestrogens such as fulvestrant, raloxifene, tamoxifen, and    toremifine,-   LHRH agonists and antagonists such as buserelin, goserelin,    leuprolide, and triptorelin,-   progestins such as medroxyprogesterone acetate and megestrol    acetate, and-   thyroid hormones such as levothyroxine and liothyronine; and-   miscellaneous agents, including altretamine, arsenic trioxide,    gallium nitrate, hydroxyurea, levamisole,-   mitotane, octreotide, procarbazine, suramin, thalidomide,    lenalidomide, photodynamic compounds such as methoxsalen and sodium    porfimer, and proteasome inhibitors such as bortezomib.

Molecular targeted therapy agents include:

-   functional therapeutic agents, including:-   gene therapy agents,-   antisense therapy agents,-   tyrosine kinase inhibitors such as erlotinib hydrochloride,    gefitinib, imatinib mesylate, and semaxanib, and-   gene expression modulators such as the retinoids and rexinoids, e.g.    adapalene, bexarotene, trans-retinoic-   acid, 9-cis-retinoic acid, and N-(4-hydroxyphenyl)retinamide;-   phenotype-directed therapy agents, including:-   monoclonal antibodies such as alemtuzumab, bevacizumab, cetuximab,    ibritumomab tiuxetan,-   rituximab, and trastuzumab,-   immunotoxins such as gemtuzumab ozogamicin,-   radio immunoconjugates such as ¹³¹I-tositumomab, and-   cancer vaccines.

Biologic therapy agents include:

-   interferons such as interferon-α_(2a) and interferon-α_(2b), and-   interleukins such as aldesleukin, denileukin diftitox, and    oprelvekin.

In addition to these agents intended to act against cancer cells,anticancer therapies include the use of protective or adjunctive agents,including:

-   cytoprotective agents such as amifostine, dexrazoxane, and mesna,-   phosphonates such as pamidronate and zoledronic acid, and-   stimulating factors such as epoetin, darbeopetin, filgrastim,    PEG-filgrastim, and sargramostim.

Combination anticancer therapy regimens to which the GST-activatedanticancer compound may be used to sensitize a mammal to and/or forwhich the GST-activated anticancer compound can be used to ameliorate aside effect of that therapy include all regimens involving the use oftwo or more of the anticancer therapies (anticancer agents) such asthose mentioned in paragraphs [0034] to [0037] above and/orradiotherapy, optionally including protective and adjunctive agents suchas those mentioned in paragraph [0038] above; and the GST-activatedanticancer compound can be used to sensitize a mammal to and/orameliorate a side effect of existing anticancer regimens known for thetreatment of various cancers, such as the regimens mentioned inparagraph [0007] above.

Many combination chemotherapeutic regimens are known to the art, such ascombinations of platinum compounds and taxanes, e.g.carboplatin/paclitaxel, capecitabine/docetaxel, the “Cooper regimen”,fluorouracil-levamisole, fluorouracil-leucovorin,methotrexate-leucovorin, and those known by the acronyms ABDIC, ABVD,AC, ADIC, AI, BACOD, BACOP, BVCPP, CABO, CAD, CAE, CAF, CAP, CD, CEC,CF, CHOP, CHOP+rituximab, CIC, CMF, CMFP, CyADIC, CyVADIC, DAC, DVD,FAC, FAC-S, FAM-S, FOLFOX-4, FOLFOX-6, M-BACOD, MACOB-B, MAID, MOPP,MVAC, PCV, T-5, VAC, VAD, VAPA, VAP-Cyclo, VAP-II, VBM, VBMCP, VIP, VP,and the like.

Combinations of chemotherapies and molecular targeted therapies,biologic therapies, and radiation therapies are also well known to theart; including therapies such as trastuzumab+paclitaxel, alone or infurther combination with carboplatin, for certain breast cancers, andmany other such regimens for other cancers; and the “Dublin regimen”(555 mg/m² fluorourac IV over 16 hours on days 1-5 and 75 mg/m²cisplatin IV over 8 hours on day 7, with repetition at 6 weeks, incombination with 40 Gy radiotherapy in 15 fractions over the first 3weeks) and the “Michigan regimen” (fluorouracil+cisplatin+vinblastine+radiotherapy), both for esophageal cancer, andmany other such regimens for other cancers.

Sensitization To Another Anticancer Therapy And/Or Amelioration Of ASide Effect Of Another Anticancer Therapy By Treatment With AGST-Activated Anticancer Compound

This invention is a method of sensitizing a mammal, especially a human,to another anticancer therapy, comprising administering a sensitizingeffective amount of a GST-activated anticancer compound to the mammal;and is also a method of ameliorating a side effect of another anticancertherapy in a mammal, especially a human, comprising administering anameliorating effective amount of a GST-activated anticancer compound tothe mammal.

A “sensitizing effective amount” of the GST-activated anticancercompound means that amount which, when administered to a mammal,especially a human, for treating a cancer with another anticancertherapy, is sufficient to sensitize the mammal to the another anticancertherapy. “Sensitizing” or “sensitization” of a mammal to anotheranticancer therapy includes one or both of:

-   (1) increasing the efficacy of the another anticancer therapy in a    mammal naive to that therapy (“initial sensitization”), and-   (2) increasing the efficacy of the another anticancer therapy in a    mammal that has already received that therapy, in particular in a    mammal that has received that therapy and been refractory or become    resistant to it (“resensitization”).

In the case of initial sensitization, increasing the efficacy of theanother anticancer therapy includes causing the therapeuticallyeffective amount of that another anticancer therapy to be lower than itwould be if the initial sensitization had not occurred (so that a lesserdose and/or reduced frequency of dosing can be used to achieve the sameanticancer effect, thereby achieving equally effective therapy with thatanother anticancer therapy with no or fewer side effects), causing theamount of the another anticancer therapy that is therapeuticallyeffective if the initial sensitization had not occurred to be moreeffective (so that a greater anticancer effect is achieved at the sameamount of the another anticancer therapy), and/or inhibiting thedevelopment of resistance to the another anticancer therapy (preventing,delaying the onset of, and/or limiting the extent of resistance to thattherapy). In the case of resensitization, increasing the efficacy of theanother anticancer therapy includes these same effects described forinitial sensitization, and particularly includes enabling thetherapeutically effective reuse of another anticancer therapy to whichresistance has developed (enabling the re-treating of a cancer withanother anticancer therapy that, prior to the resensitization, hadbecome resistant or refractory to that therapy).

An “ameliorating effective amount” of the GST-activated anticancercompound means that amount which, when administered to a mammal,especially a human, being treated for a cancer with another anticancertherapy, is sufficient to ameliorate one or more of the side effects ofthe another anticancer therapy. “Ameliorating” or “amelioration” of aside effect of another anticancer therapy includes one or more of:

-   (1) preventing the occurrence of that side effect; and-   (2) limiting the severity of that side effect.

The side effects that may be ameliorated by treatment with theGST-activated anticancer compound may include any one or more of theknown side effects of the another anticancer therapy. Such side effectsinclude alopecia, nausea and/or vomiting, hematologic side effects suchas neutropenia, neurologic side effects such as peripheral neuropathy,and the like.

A “therapeutically effective amount” of the another anticancer therapymeans that amount which, when administered to a mammal, especially ahuman, for treating a cancer, is sufficient to effect treatment for thecancer. “Treating” or “treatment” of a cancer in a mammal includes oneor more of:

-   (1) inhibiting growth of the cancer, i.e., arresting its    development,-   (2) preventing spread of the cancer, i.e. preventing metastases,-   (3) relieving the cancer, i.e., causing regression of the cancer,-   (4) preventing recurrence of the cancer, and-   (5) palliating symptoms of the cancer.

Cancers which may be effectively treated by the method of this inventioninclude mammalian cancers, especially human cancers. Cancers that areparticularly treatable by the method of this invention are cancers withsensitivity to inducers of apoptosis, and more specifically thosecancers that express or, particularly, overexpress one or moreglutathione S-transferase isoenzymes. Cancers that express oroverexpress one or more glutathione S-transferase isoenzymes whentreated with other anticancer compounds or combination anticancerchemotherapy regimens (i.e. those not including a GST-activatedanticancer compound) are especially treatable by the method of thisinvention. Such cancers include cancers of the brain, breast, bladder,cervix, colon and rectum, esophagus, head and neck, kidney, lung, liver,ovary, pancreas, prostate, and stomach; leukemias such as ALL, AML,AMML, CLL, CML, CMML, and hairy cell leukemia; Hodgkin's andnon-Hodgkin's lymphomas; mesotheliomas, multiple myeloma; and sarcomasof bone and soft tissue. Cancers particularly treatable by the method ofthis invention with canfosfamide and its salts as the GST-activatedanticancer compound include breast, ovarian, colorectal, and non-smallcell lung cancers; and TLK296 would also be useful for the same cancersbecause it also is activated by GST P1-1. Other GST-activated anticancercompounds are expected to be suitable for these or other cancersdepending on the nature of the GST isoenzymes expressed by the cancerbeing treated.

Another anticancer therapies which may particularly benefit from thesensitization and/or amelioration method of this invention are thosetherapies where one or more GST isoenzymes are implicated in the actionof that anticancer therapy; and particularly therapies involving theadministration of platinum compounds such as cisplatin, carboplatin,oxaliplatin, satraplatin, and picoplatin, especially cisplatin andcarboplatin; taxanes, such as paclitaxel and docetaxel; andanthracyclines such as daunorubicin, doxorubicin, epirubicin,idarubicin, and valrubicin. Thus the method of this inventionparticularly includes the sensitization to anticancer therapiesinvolving platinum compounds, taxanes, and anthracyclines byadministering a GST-activated anticancer compound of this invention; andthe amelioration of a side effect, such as alopecia, of anticancertherapies involving platinum compounds, taxanes, and anthracyclines by aGST-activated anticancer compound of this invention.

The method of this invention therefore also comprises the administrationof a sensitizing and/or ameliorating effective amount of a GST-activatedanticancer compound and a therapeutically active amount of anotheranticancer therapy. The another anticancer therapy will generally be onethat has utility in the treatment of the cancer being treated evenwithout the sensitization and/or amelioration effect of theGST-activated anticancer compound; and a suitable such anotheranticancer therapy for a particular cancer to be treated will bedeterminable by a person of ordinary skill in the art having regard tothat knowledge and this disclosure. It is of course contemplated thatthe sensitization and/or amelioration therapy of this invention may beused with anticancer therapies not yet in use. The GST-activatedanticancer agent may also be used as adjuvant or neoadjuvant therapyaccompanying radiation therapy.

For sensitization, the amount of the GST-activated anticancer compoundthat is administered to the mammal should be a sensitizing effectiveamount for the another anticancer therapy; and similarly the amount ofthe another anticancer therapy that is administered to the mammal shouldbe a therapeutically effective amount when the mammal has beensensitized with the GST-activated anticancer compound. However, thesensitizing effective amount of the GST-activated anticancer compoundmay be different depending on the another anticancer therapy; and thetherapeutically effective amount of the another anticancer therapy whenadministered in the method of this invention may be less than the amountwhich would be therapeutically effective if delivered to the mammalwithout sensitization. It is common in cancer therapy, though, to usethe maximum tolerated dose of the or each therapy, with a reduction onlybecause of common toxicity of the therapies used or potentiation of thetoxicity of one therapy by another. Because of the lack ofcross-resistance of canfosfamide and its salts, especially canfosfamidehydrochloride, for example, with several common chemotherapeutic agents,and its relative lack of clinically severe toxicity, especially its lackof clinically severe hematological toxicity, it is expected that noreduction in the amount of the another anticancer therapy will berequired.

For amelioration, the amount of the GST-activated anticancer compoundthat is administered to the mammal should be an ameliorating effectiveamount for the another anticancer therapy; and similarly the amount ofthe another anticancer therapy that is administered to the mammal shouldbe a therapeutically effective amount when a side effect has beenameliorated with the GST-activated anticancer compound. However, theameliorating effective amount of the GST-activated anticancer compoundmay be different depending on the another anticancer therapy; and thetherapeutically effective amount of the another anticancer therapy whenadministered in the method of this invention may be less than the amountwhich would be therapeutically effective if delivered to the mammalwithout amelioration (since the GST-activated anticancer compound mayalso sensitize the mammal to that another anticancer therapy, asdiscussed elsewhere in this application). It is common in cancertherapy, though, to use the maximum tolerated dose of the or eachtherapy, with a reduction only because of common toxicity of thetherapies used or potentiation of the toxicity of one therapy byanother. Because of the lack of cross-resistance of canfosfamide and itssalts, especially canfosfamide hydrochloride, for example, with severalcommon chemotherapeutic agents, and its relative lack of clinicallysevere toxicity, especially its lack of clinically severe hematologicaltoxicity, it is expected that no reduction in the amount of the anotheranticancer therapy will be required; and the amount of the anotheranticancer therapy that may be able to be administered may be higherthan the usual dosage because of the amelioration of a side effect ofthat another anticancer therapy provided by the GST-activated anticancercompound.

The sensitization and/or amelioration therapy may involve theadministration of the GST-activated anticancer compound before or duringthe administration of the another anticancer therapy. The administrationof the GST-activated anticancer compound may precede at least one aspectof the another anticancer therapy (such as the administration of onedose of a chemotherapeutic agent, molecular targeted therapy agent,biologic therapy agent, or radiation therapy) by as little as a fewminutes (for example, during the same day, e.g. during the sametreatment visit) to as much as several weeks, for example from one tofive weeks, e.g. one to three weeks.

Although not wishing to be bound by theory, it is considered thatsensitization and/or amelioration therapy with the GST-activatedanticancer compound, particularly a GST P1-1 activated anticancercompound such as canfosfamide and its salts, especially canfosfamidehydrochloride, and another anticancer therapy will be of benefit becauseof one or both of the following mechanisms:

(1) GST P1-1 is overexpressed in many cancer cell lines, andparticularly in cell lines treated with known anticancer therapies suchas treatment with platinum-containing compounds and doxorubicin; and theincrease in GST P1-1 is correlated with an increase in resistance to theanticancer therapy. Because compounds such as canfosfamide are activatedby GST P1-1, cancer cells that have been treated with another anticancertherapy will contain an elevated level of GST P1-1 and will thereforeincrease the activity of canfosfamide in these cells. Thus aGST-activated anticancer compound such as canfosfamide or its salt willbe especially potent in resensitization and in sensitization in cancercells that already overexpress GST P1-1. Likewise other GST-activatedanticancer compounds activated by other GST isoenzymes may be especiallyeffective as sensitizers in cancers in which those other GST isoenzymesare implicated; and

(2) Compounds such as canfosfamide are activated by GST P1-1, and thisactivation is achieved by interaction of the canfosfamide with theactive site of the enzyme. This interaction will limit the ability ofthe enzyme to interact with and detoxify other anticancer agents whichmight otherwise be detoxified by GST P1-1, thereby effectivelyincreasing the cytotoxicity of (reducing the therapeutically effectiveamount of) these other anticancer agents. Thus administration of aGST-activated anticancer compound such as canfosfamide or its salt as asensitizing agent will make the another anticancer therapy moreeffective than it would have been without the sensitization, and mayre-enable use of another anticancer therapy to which the cancer hasbecome resistant or refractory. In particular, because certain of theseGST-activated anticancer compounds, such as canfosfamide, areirreversible inhibitors of GST P1-1, they may be especially effective inthe sensitization method of this invention. Likewise, otherGST-activated anticancer compounds interacting with and/or inhibitingother GST isoenzymes may be especially effective as sensitizers incancers in which those other GST isoenzymes are implicated. Insofar asthe toxicities (side effects) of any of the another anticancer therapiesmay be influenced by the interaction of the another anticancer therapieswith a GST isoenzyme (such as GST P1-1), inhibition of the GSTisoenzymes may also ameliorate a side effect of that another anticancertherapy, and thus GST-activated anticancer compounds like canfosfamideand its salts may be especially effective as ameliorators of the sideeffects of these anticancer therapies.

Suitable sensitization and/or amelioration dosing for canfosfamide orits salt as the GST-activated anticancer compound may be the same as theusual therapeutic dose, but will preferably be below the usualtherapeutic dose, such as about 5-75% of the usual therapeutic dose,e.g. about 10-50% of the usual therapeutic dose, such as 20%, 25%, or30% of the usual therapeutic dose; for example about 60-450 mg/m² bodysurface area, especially 125-450 mg/m² for canfosfamide hydrochloride.Dosing may be at 1-35 day intervals; for example, about 125-450 mg/m² at1-5 week intervals, especially at 1, 2, 3, or 4 week intervals, or athigher frequencies including as frequently as once/day for several (e.g.5 or 7) days, with the dosing repeated every 2, 3, or 4 weeks, orconstant infusion for a period of 6-72 hours, also with the dosingrepeated every 2, 3, or 4 weeks; and such dosing flexibility willreadily enable sensitization and/or amelioration for the anticancertherapies now used. Suitable dosages and dose frequencies for otherGST-activated anticancer compounds will also preferably be below theusual therapeutic dose, such as about 5-50% of the usual therapeuticdose, e.g. 10-50% of the usual therapeutic dose, and will be readilydeterminable by a person of ordinary skill in the art having regard tothat skill and this disclosure.

Suitable dosing for the other anticancer therapy will be the dosingalready established for that therapy, as described in documents such asthose cited in paragraph [0007], recognizing that the therapeuticallyeffective amount of the another anticancer therapy may be reduced by thesensitization of this invention. Such dosing varies widely with thetherapy: for example, capecitabine (2500 mg/m² orally) is dosed twicedaily for 2 weeks on and 1 week off, imatinib mesylate (400 or 600mg/day orally) is dosed daily, rituximab is dosed weekly, paclitaxel(135-175 mg/m² and docetaxel (60-100 mg/m²) are dosed weekly to everythree weeks, carboplatin (4-6 mg/mL·min) is dosed once every 3 or 4weeks (though the doses may be split and administered over severaldays), nitrosourea alkylating agents such as carmustine are dosed asinfrequently as once every 6 weeks. Radiotherapy may be administered asfrequently as weekly (or even within that split into smaller dosagesadministered daily).

A person of ordinary skill in the art of anticancer therapy will be ableto ascertain a sensitizing and/or ameliorating effective amount of theGST-activated anticancer compound and a therapeutically effective amountof another anticancer therapy for a given cancer and stage of diseasewithout undue experimentation and in reliance upon personal knowledgeand the disclosure of this application.

The GST-activated anticancer compound and the another anticancer therapymay be administered by any route suitable to the subject being treatedand the nature of the subject's condition. Routes of administrationinclude, but are not limited to, administration by injection, includingintravenous, intraperitoneal, intramuscular, and subcutaneous injection,by transmucosal or transdermal delivery, through topical applications,nasal spray, suppository and the like or may be administered orally.Formulations may optionally be liposomal formulations, emulsions,formulations designed to administer the drug across mucosal membranes ortransdermal formulations. Suitable formulations for each of thesemethods of administration may be found, for example, in Remington: TheScience and Practice of Pharmacy, 20th ed., A. Gennaro, ed., LippincottWilliams & Wilkins, Philadelphia, Pa., U.S.A. Typical formulations willbe either oral (as for compounds such as capecitabine) or solutions forintravenous infusion. Typical dosage forms will be tablets (for oraladministration), solutions for intravenous infusion, and lyophilizedpowders for reconstitution as solutions for intravenous infusion.Although anticancer therapies are usually administered systemically, itis contemplated that the GST-activated anticancer compound may also beadministered regionally, such as peritumorally or intratumorally, tosensitize the cancer to the another anticancer therapy administeredeither systemically or regionally.

Another anticancer therapies considered of particular present interestfor sensitization or side effect amelioration by the method of thisinvention, especially with canfosfarnide or its salt, include: aplatinum compound such as carboplatin or cisplatin, optionally incombination with gemcitabine or a taxane such as docetaxel orpaclitaxel; with gemcitabine; a taxane; an anthracycline such asdoxorubicin or liposomal doxorubicin; oxaliplatin, optionally incombination with capecitabine or fluorouracil/leucovorin; andgemcitabine or a platinum compound such as carboplatin or cisplatin, incombination with a vinca alkaloid such as vinorelbine. It will be seenfrom the in vitro example that follows that canfosfamide hydrochloridecauses sensitization to paclitaxel and, as mentioned previously, it isexpected that canfosfamide or its salts or other GST-activatedanticancer compounds can be used to sensitize to other anticancertherapies generally; and it will be seen from the clinical observationthat follows that canfosfamide hydrochloride ameliorates the alopeciaside effect of carboplatin and, as mentioned previously, it is expectedthat canfosfamide and its salts or other GST-activated anticancercompounds can be used to ameliorate a side effect of other anticancertherapies generally.

In vitro example

The following example illustrates the beneficial effect of canfosfamide,a GST-activated anticancer compound, in sensitizing human cancer celllines in vitro to the effect of another anticancer agent. This result isconsidered predictive of efficacy in human anticancer chemotherapy, aseach of canfosfamide and the other anticancer agent tested have shownanticancer activity in humans.

Cancer cell line. The human cancer cell line OVCAR-3 (ovarianadenocarcinoma) was obtained from the National Cancer Institute,Bethesda, Md., U.S.A.

Anticancer compounds. Canfosfamide was prepared for Telik. Paclitaxelwas obtained from Sigma-Aldrich Chemical Company, St. Louis, Mo., U.S.A.

EXAMPLE 1 Canfosfamide Hydrochloride And Paclitaxel

A paclitaxel-resistant derivative cell line OVCAR-PR was developed fromthe human ovarian cancer cell line OVCAR-3 by growing OVCAR-3 cells ingradually increasing concentrations (up to 5 nM) of paclitaxel. Acanfosfamide-modified derivative cell line OVCAR-TLK was developed bygrowing OVCAR-3 cells in gradually increasing concentrations (up to 6.5μM) of canfosfamide. To maintain the phenotypes of the cell lines, thecells were treated with the compounds at weekly intervals. Cells weregrown in compound-free media for 24 hours before any experiments.

Cytotoxicity assay. Log-phase cells were seeded in 96-well plates andincubated with the diluted compound or solvent for 2-3 doubling times.The extent of cell growth was quantitated using the CellTiter-Glo assay(Promega Corporation, Madison, Wis., U.S.A.), used in accordance withthe assay kit directions. The amount of ATP in the lysate, whichcorresponds to the number of viable cells, was quantitated using aluminometer. All assays were conducted in triplicate wells, with solventcontrol. The extent of cell growth was expressed as a percentage of thesignal from the solvent control wells. The mean of the triplicate wellswas computed and IC₅₀ determined using PrismGraph.

Cell doubling time. 1.5×10⁴ cells were seeded in a 25-mL flask. Thecells were grown for four days and the number of viable cells wasdetermined by Trypan Blue staining and manual counting using ahemocytometer. The assay was conducted in triplicate at each time point.The times for two cell doublings for OVCAR-3 and OVCAR-TLK cells wereapproximately 3.5 and 5.5 days, respectively.

Results: The IC₅₀ for paclitaxel increased from 1.3 nM in OVCAR-3- cellsto 49 nM in OVCAR-PR cells, a more than 35-fold increase in resistance.However, the IC₅₀ for canfosfamide increased from 1.3 μM in OVCAR-3cells to only 1.6 μM nM in OVCAR-PR cells, only a 1.2-fold increase inresistance. When the OVCAR-PR cells were first treated overnight with 4μM canfosfamide, then tested for their response to paclitaxel, the IC₅₀for paclitaxel decreased approximately 3-fold, indicating sensitizationof these formerly paclitaxel-resistant cells by treatment withcanfosfamide. When OVCAR-3 and OVCAR-TLK cells were treated withpaclitaxel for equal treatment times, the IC₅₀s for paclitaxel wereapproximately the same, but when the cells were treated for treatmenttimes adjusted for the differential doubling times (treated forapproximately two doubling times), the IC₅₀ for paclitaxel of was about2-fold lower in the OVCAR-TLK cells, indicating sensitization of eventhese non-paclitaxel-resistant cells by treatment with canfosfamide.OVCAR-3 and OVCAR-TLK cells were approximately equally sensitive tocanfosfamide when treated for approximately two doubling times.

Therapeutic Examples

Sensitization To Another Anticancer Therapies With Canfosfanide

Canfosfamide at an initial dose of 500 mg/m² is administeredintravenously, followed 30 minutes later by the intravenousadministration of oxaliplatin at a therapeutically effective dose suchas 85 mg/m². The canfosfamide dose may be increased to 850 mg/m² andfurther to 1280 mg/m², and the oxaliplatin dose may also be varied. Thiscombination is administered at 2-weekly intervals.

Canfosfamide at an initial dose of 500 mg/m² is administeredintravenously at 3-weekly intervals, accompanied by the oraladministration of capecitabine at a therapeutically effective dose suchas 1250 mg/m² twice/day for 14 days, followed by 7 days withouttreatment. The canfosfamide dose may be increased to 750 mg/m² andfurther to 960 mg/m², and the capecitabine dose may also be varied.

Canfosfamide at an initial dose of 400 mg/m² is administeredintravenously at 2-weekly intervals, followed 30 minutes later by theintravenous administration of fluorouracil at a therapeuticallyeffective dose such as 12 mg/Kg, with leucovorin rescue after completionof four days of fluorouracil therapy. The canfosfamide dose may beincreased to 700 mg/m² and further to 1000 mg/m², and the fluorouracildose may also be varied.

Ovarian cancer patients treated with carboplatin-containing regimensunderwent repeated cycles of alopecia corresponding to theadministration of the carboplatin. The same patients, when treated withcarboplatin at AUC 5 or 6 mg/mL·min in combination with canfosfamidehydrochloride at 500 mg/m² and carboplatin at AUC 6 mg/mL·min incombination with canfosfamide hydrochloride at 750, and 960 mg/M² didnot experience the same recurrence of alopecia with treatment,illustrating the amelioration of this side effect of carboplatin therapyby treatment with canfosfamide hydrochloride. Other side effects such asthe hematologic and neurologic side effects of carboplatin weresimilarly ameliorated.

Other GST-activated anticancer compounds may be used similarly in themethods of this invention. Different other anticancer therapies, such asother chemotherapies, molecularly targeted therapies, biologictherapies, and radiation therapies may also be used similarly in themethods of this invention and will benefit from the sensitization and/orside effect amelioration induced by treatment with the GST-activatedanticancer compounds.

While this invention has been described in conjunction with specificembodiments and examples, it will be apparent to a person of ordinaryskill in the art, having regard to that skill and this disclosure, thatequivalents of the specifically disclosed materials and methods willalso be applicable to this invention; and such equivalents are intendedto be included within the following claims.

1. A method of sensitizing a mammal to another anticancer therapycomprising administering a sensitizing effective amount of aGST-activated anticancer compound.
 2. The method of claim 1 where themammal is a human.
 3. The method of claim 2 where the GST-activatedanticancer compound is a compound of the formula

or an amide, ester, or salt thereof, where: L is a cytotoxic electronwithdrawing leaving group; S^(x) is —S(═O)—, —S(═O)₂—, —S(═NH)—,—S(═O)(═NH)—, —S⁺(C₁-C₆ alkyl)—, —Se(═O)—, —Se(═O)₂—, —Se(═NH)—, or—Se(═O)(═NH)—, or is —O—C(═O)—, or —HN—C(═O)—; each of R¹, R² and R³ isindependently H or a non-interfering substituent; n is 0, 1 or 2; Y isselected from the group consisting of

where m is 1 or 2; and AA_(c) is an amino acid linked through a peptidebond to the remainder of the compound.
 4. The method of claim 3 wherethe GST-activated anticancer compound is canfosfamide or a salt thereof.5. The method of claim 4 where the GST-activated anticancer compound iscanfosfamide hydrochloride.
 6. The method of claim 1 where the anotheranticancer therapy is selected from one or more of chemotherapy,molecular targeted therapy, biologic therapy, and radiotherapy.
 7. Themethod of claim 6 where the another anticancer therapy is administrationof one or more of an alkylating agent, an antimetabolite, a naturalproduct, a hormone or hormone antagonist, a miscellaneous agent, afunctional therapeutic agent, a gene therapy agent, an antisense therapyagent, a tyrosine kinase inhibitor, a gene expression modulator, aphenotype-directed therapy agent, a monoclonal antibody, an immunotoxin,a radioimmunoconjugate, a cancer vaccine, an interferon, and aninterleukin.
 8. The method of claim 7 where the another anticancertherapy is administration of one or more of busulfan, thiotepa,chlorambucil, cyclophosphamide, estramustine, ifosfamide,mechlorethamine, melphalan, uramustine, carmustine, lomustine,streptozocin, dacarbazine, procarbazine, temozolamide, cisplatin,carboplatin, oxaliplatin, satraplatin, picoplatin, methotrexate,permetrexed, raltitrexed, trimetrexate, cladribine,chlorodeoxyadenosine, clofarabine, fludarabine, mercaptopurine,pentostatin, thioguanine, azacitidine, capecitabine, cytarabine,edatrexate, floxuridine, fluorouracil, gemcitabine, troxacitabine,bleomycin, dactinomycin, mithramycin, mitomycin, mitoxantrone,porfiromycin, daunorubicin, daunorubicin, doxorubicin, liposomaldoxorubicin, epirubicin, idarubicin, valrubicin, L-asparaginase,PEG-L-asparaginase, paclitaxel, docetaxel, vinblastine, vincristine,vindesine, vinorelbine, irinotecan, topotecan, amsacrine, etoposide,teniposide, fluoxymesterone, testolactone, bicalutamide, cyproterone,flutamide, nilutamide, aminoglutethimide, anastrozole, exemestane,formestane, letrozole, dexamethasone, prednisone, diethylstilbestrol,fulvestrant, raloxifene, tamoxifen, toremifine, buserelin, goserelin,leuprolide, triptorelin, medroxyprogesterone acetate, megestrol acetate,levothyroxine, liothyronine, altretamine, arsenic trioxide, galliumnitrate, hydroxyurea, levamisole, mitotane, octreotide, procarbazine,suramin, thalidomide, lenalidomide, methoxsalen, sodium porfimer,bortezomib, erlotinib hydrochloride, gefitinib, imatinib mesylate,semaxanib, adapalene, bexarotene, trans-retinoic acid, 9-cis-retinoicacid, and N-(4-hydroxyphenyl)retinamide, alemtuzumab, bevacizumab,cetuximab, ibritumomab tiuxetan, rituximab, trastuzumab, gemtuzumabozogamicin, ¹³¹I-tositumomab, interferon-α_(2a), interferon-α_(2b),aldesleukin, denileukin diftitox, and oprelvekin.
 9. The method of claim8 where the another anticancer therapy is administration of: a platinumcompound, optionally in further combination with gemcitabine or ataxane; gemcitabine; a taxane; an anthracycline; oxaliplatin, optionallyin further combination with capecitabine or fluorouracil/leucovorin; andgemcitabine or a platinum compound, in further combination with a vincaalkaloid.
 10. The method of claim 9 where the another anticancer therapyis administration of cisplatin or carboplatin.
 11. The method of claim10 where the another anticancer therapy is administration of cisplatinor carboplatin as sole therapy.
 12. The method of claim 6 where theanother anticancer therapy is administration of two or more ofchemotherapy, molecular targeted therapy, biologic therapy; orradiotherapy.
 13. The method of claim 6 where the another anticancertherapy is administration of two or more chemotherapy agents.
 14. Themethod of claim 6 where the another anticancer therapy includesradiation therapy.
 15. The method of claim 14 where the anotheranticancer therapy is radiation therapy.
 16. The method of claim 1 wherethe dosing of the GST-activated anticancer compound is about 5-50%,especially about 10-50%, of the usual therapeutic dose of thatGST-activated anticancer compound, at 1-35 day intervals.
 17. The methodof claim 16 where the dosing is at 1-5 week intervals, especially at 1,2, 3, or 4 week intervals.
 18. The method of claim 16 where theGST-activated anticancer compound is canfosfamide hydrochloride and thedosing is about 125-450 mg/m² at 1-5 week intervals, especially at 1, 2,3, or 4 week intervals.
 19. A method of ameliorating a side effect ofanother anticancer therapy in a mammal comprising administering anameliorating effective amount of a GST-activated anticancer compound.20. The method of claim 19 where the mammal is a human.
 21. The methodof claim 20 where the GST-activated anticancer compound is a compound ofthe formula

or an amide, ester, or salt thereof, where: L is a cytotoxic electronwithdrawing leaving group; S^(x) —S(═O)—, —S(═O)₂—, —S(═NH)—,—S(═O)(═NH)—, —S⁺(C₁-C₆ alkyl)—, —Se(═O)—, —Se(═O)₂—, —Se(═NH)—, or—Se(═O)(═NH)—, or is —O—C(═O)—, or —HN—C(═O)—; each of R¹, R² and R³ isindependently H or a non-interfering substituent; n is 0, 1 or 2; Y isselected from the group consisting of

where m is 1 or 2; and AA_(c) is an amino acid linked through a peptidebond to the remainder of the compound.
 22. The method of claim 21 wherethe GST-activated anticancer compound is canfosfamide or a salt thereof.23. The method of claim 22 where the GST-activated anticancer compoundis canfosfamide hydrochloride.
 24. The method of claim 19 where theanother anticancer therapy is selected from one or more of chemotherapy,molecular targeted therapy, biologic therapy, and radiotherapy.
 25. Themethod of claim 24 where the another anticancer therapy isadministration of one or more of an alkylating agent, an antimetabolite,a natural product, a hormone or hormone antagonist, a miscellaneousagent, a functional therapeutic agent, a gene therapy agent, anantisense therapy agent, a tyrosine kinase inhibitor, a gene expressionmodulator, a phenotype-directed therapy agent, a monoclonal antibody, animmunotoxin, a radioimmunoconjugate, a cancer vaccine, an interferon,and an interleukin.
 26. The method of claim 25 where the anotheranticancer therapy is administration of one or more of busulfan,thiotepa, chlorambucil, cyclophosphamide, estramustine, ifosfamide,mechlorethamine, melphalan, uramustine, carmustine, lomustine,streptozocin, dacarbazine, procarbazine, temozolamide, cisplatin,carboplatin, oxaliplatin, satraplatin, picoplatin, methotrexate,permetrexed, raltitrexed, trimetrexate, cladribine,chlorodeoxyadenosine, clofarabine, fludarabine, mercaptopurine,pentostatin, thioguanine, azacitidine, capecitabine, cytarabine,edatrexate, floxuridine, fluorouracil, gemcitabine, troxacitabine,bleomycin, dactinomycin, mithramycin, mitomycin, mitoxantrone,porfiromycin, daunorubicin, daunorubicin, doxorubicin, liposomaldoxorubicin, epirubicin, idarubicin, valrubicin, L-asparaginase,PEG-L-asparaginase, paclitaxel, docetaxel, vinblastine, vincristine,vindesine, vinorelbine, irinotecan, topotecan, amsacrine, etoposide,teniposide, fluoxymesterone, testolactone, bicalutamide, cyproterone,flutamide, nilutamide, aminoglutethimide, anastrozole, exemestane,formestane, letrozole, dexamethasone, prednisone, diethylstilbestrol,fulvestrant, raloxifene, tamoxifen, toremifine, buserelin, goserelin,leuprolide, triptorelin, medroxyprogesterone acetate, megestrol acetate,levothyroxine, liothyronine, altretamine, arsenic trioxide, galliumnitrate, hydroxyurea, levamisole, mitotane, octreotide, procarbazine,suramin, thalidomide, lenalidomide, methoxsalen, sodium porfimer,bortezomib, erlotinib hydrochloride, gefitinib, imatinib mesylate,semaxanib, adapalene, bexarotene, trans-retinoic acid, 9-cis-retinoicacid, and N-(4-hydroxyphenyl)retinamide, alemtuzumab, bevacizumab,cetuximab, ibritumomab tiuxetan, rituximab, trastuzumab, gemtuzumabozogamicin, ¹³¹I-tositumomab, interferon-α_(2a), interferon-α_(2b),aldesleukin, denileukin diftitox, and oprelvekin.
 27. The method ofclaim 26 where the another anticancer therapy is administration of: aplatinum compound, optionally in further combination with gemcitabine ora taxane; gemcitabine; a taxane; an anthracycline; oxaliplatin,optionally in further combination with capecitabine orfluorouracil/leucovorin; and gemcitabine or a platinum compound, infurther combination with a vinca alkaloid.
 28. The method of claim 27where the another anticancer therapy is administration of cisplatin orcarboplatin.
 29. The method of claim 28 where the another anticancertherapy is administration of cisplatin or carboplatin as sole therapy.30. The method of claim 24 where the another anticancer therapy isadministration of two or more of chemotherapy; molecular targetedtherapy; biologic therapy; and radiotherapy.
 31. The method of claim 24where the another anticancer therapy is administration of two or morechemotherapy agents.
 32. The method of claim 24 where the anotheranticancer therapy includes radiation therapy.
 33. The method of claim32 where the another anticancer therapy is radiation therapy.
 34. Themethod of claim 19 where the dosing of the GST-activated anticancercompound is about 5-50%, especially about 10-50%, of the usualtherapeutic dose of that GST-activated anticancer compound, at 1-35 dayintervals.
 35. The method of claim 34 where the dosing is at 1-5 weekintervals, especially at 1, 2, 3, or 4 week intervals.
 36. The method ofclaim 34 where the GST-activated anticancer compound is canfosfamidehydrochloride and the dosing is about 125-450 mg/m² at 1-5 weekintervals, especially at 1, 2, 3, or 4 week intervals.
 37. Apharmaceutical composition for sensitizing a mammal, especially a human,to another anticancer therapy, comprising a sensitizing effective amountof a GST-activated anticancer compound and an excipient.
 38. Thecomposition of claim 37 where the GST-activated anticancer compound is acompound of the formula

or an amide, ester, or salt thereof, where: L is a cytotoxic electronwithdrawing leaving group; S^(x) is —S(═O)—, —S(═O)₂—, —S(═NH)—,—S(═O)(═NH)—, —S⁺(C₁-C₆ alkyl)—, —Se(═O)—, —Se(═O)₂—, —Se(═NH)—, or—Se(═O)(═NH)—, or is —O—C(═O)—, or —HN—C(═O)—; each of R¹, R² and R³ isindependently H or a non-interfering substituent; n is 0, 1 or 2; Y isselected from the group consisting of

where m is 1 or 2; and AA_(c) is an amino acid linked through a peptidebond to the remainder of the compound.
 39. The composition of claim 38where the GST-activated anticancer compound is canfosfamide or a saltthereof.
 40. The composition of claim 39 where the GST-activatedanticancer compound is canfosfamide hydrochloride.
 41. A pharmaceuticalcomposition for ameliorating a side effect of another anticancer therapyin a mammal, especially a human, comprising an ameliorating effectiveamount of a GST-activated anticancer compound and an excipient.
 42. Thecomposition of claim 41 where the GST-activated anticancer compound is acompound of the formula

or an amide, ester, or salt thereof, where: L is a cytotoxic electronwithdrawing leaving group; S^(x) is —S(═O)—, —S(═O)₂—, —S(═NH)—,—S(═O)(═NH)—, —S⁺(C₁-C₆ alkyl)—, —Se(═O)—, —Se(═O)₂—, —Se(═NH)—, or—Se(═O)(═NH)—, or is —O—C(═O)—, or —HN—C(═O)—; each of R¹, R² and R³ isindependently H or a non-interfering substituent; n is 0, 1 or 2; Y isselected from the group consisting of

where m is 1 or 2; and AA_(c) is an amino acid linked through a peptidebond to the remainder of the compound.
 43. The composition of claim 42where the GST-activated anticancer compound is canfosfamide or a saltthereof.
 44. The composition of claim 43 where the GST-activatedanticancer compound is canfosfamide hydrochloride.